Hi, thank you so much for answering. I think she's just a crested, I'm not sure. you can see her here:
http://www.youtube.com/watch?v=l0T-0gV_Xno she's the piano playing one. (Do you think she's small? She's an adult already.)
I think she could be a runt.
The food that I feed her is Oxbow, plus they get vegetables and Vitamin C tablets (chewables for kids)
She usually walks on all fours but sometimes I catch her lifting one of her leg up when walking and it frightens me so I will pick her up and put her down and see how she walks again and she will walk properly again.
I will definitely bring her to the vet if she's sick, but if she's not sick then I don't think I want to do so. It's quite expensive.